}
-void* OS::Allocate(const size_t requested,
- size_t* allocated,
- bool is_executable) {
+static void* GetRandomAddr() {
// The address range used to randomize RWX allocations in OS::Allocate
// Try not to map pages into the default range that windows loads DLLs
// Use a multiple of 64k to prevent committing unused memory.
static const intptr_t kAllocationRandomAddressMin = 0x04000000;
static const intptr_t kAllocationRandomAddressMax = 0x3FFF0000;
#endif
+ uintptr_t address = (V8::RandomPrivate(Isolate::Current()) << kPageSizeBits)
+ | kAllocationRandomAddressMin;
+ address &= kAllocationRandomAddressMax;
+ return reinterpret_cast<void *>(address);
+}
+
+
+static void* RandomizedVirtualAlloc(size_t size, int action, int protection) {
+ LPVOID base = NULL;
+
+ if (protection == PAGE_EXECUTE_READWRITE || protection == PAGE_NOACCESS) {
+ // For exectutable pages try and randomize the allocation address
+ for (size_t attempts = 0; base == NULL && attempts < 3; ++attempts) {
+ base = VirtualAlloc(GetRandomAddr(), size, action, protection);
+ }
+ }
+
+ // After three attempts give up and let the OS find an address to use.
+ if (base == NULL) base = VirtualAlloc(NULL, size, action, protection);
+ return base;
+}
+
+
+void* OS::Allocate(const size_t requested,
+ size_t* allocated,
+ bool is_executable) {
// VirtualAlloc rounds allocated size to page size automatically.
size_t msize = RoundUp(requested, static_cast<int>(GetPageSize()));
- intptr_t address = 0;
+ void* address = 0;
// Windows XP SP2 allows Data Excution Prevention (DEP).
int prot = is_executable ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE;
- // For exectutable pages try and randomize the allocation address
- if (prot == PAGE_EXECUTE_READWRITE &&
- msize >= static_cast<size_t>(Page::kPageSize)) {
- address = (V8::RandomPrivate(Isolate::Current()) << kPageSizeBits)
- | kAllocationRandomAddressMin;
- address &= kAllocationRandomAddressMax;
- }
-
- LPVOID mbase = VirtualAlloc(reinterpret_cast<void *>(address),
- msize,
- MEM_COMMIT | MEM_RESERVE,
- prot);
- if (mbase == NULL && address != 0)
- mbase = VirtualAlloc(NULL, msize, MEM_COMMIT | MEM_RESERVE, prot);
+ LPVOID mbase = RandomizedVirtualAlloc(msize,
+ MEM_COMMIT | MEM_RESERVE,
+ prot);
if (mbase == NULL) {
LOG(ISOLATE, StringEvent("OS::Allocate", "VirtualAlloc failed"));
void* VirtualMemory::ReserveRegion(size_t size) {
- return VirtualAlloc(NULL, size, MEM_RESERVE, PAGE_NOACCESS);
+ return RandomizedVirtualAlloc(size, MEM_RESERVE, PAGE_NOACCESS);
}
}
-
// ----------------------------------------------------------------------------
// Win32 thread support.